Diesel engine exhaust systems often include an aftertreatment system to reduce emissions. One method used to reduce emissions from a diesel engine is selective catalytic reduction (SCR). SCR provides a method for removing NOx from an exhaust stream through use of an SCR catalyst that facilitates a reaction between the exhaust gas, ammonia and NOx to produce water vapor and nitrogen gas thereby removing NOx from the exhaust gas. The ammonia used for SCR is typically stored in an ammonia storage system for injection when needed. Such on-board ammonia storage systems and the associated ammonia injection systems add cost, complexity and weight to the vehicle. Thus, while such exhaust aftertreatment systems using ammonia storage and injection work for their intended purpose, there remains a need for improvement in the relevant art.